Why is it not recommended to use an autoclave for home canning?

Asked December 16, 2020, 8:24 PM EST

Hello, I am finding many sources state the manufacturer will tell you not to use an autoclave for pressure canning but I have never found sufficient reason why and they don't provide one.

It is my understanding there isn't a particular reason other than it maybe considered inefficient due to lack of a way to vent steam automatically vent pressure with a weight on top of a vent at the appropriate 10-15 PSI and the size and thickness of the walls.

Is there be another compelling reason other than ease of use not to?

Thank you

Oregon

1 Response

Hi, Thanks for contacting Ask an Expert.

We recommend you follow the autoclave manufacturer's directions. If they are telling customers not to use an autoclave for pressure canning then their lawyers are probably behind that advice due to misuse resulting in mishaps in the past.

Likely reasons are that the autoclave heats up or cools down too quickly, or you cannot get the minimum four quart jars inside with the lid on (too small to hold enough heat). This is mainly why electric or standard pressure cookers (EPC) are not safe for pressure canning. They are designed to cool quickly so dinner can be served almost immediately. Research tells us that the natural cool down time in a pressure canner is very important because 30% of the C. botulinum spores are killed in those approximately 30 minutes.

While reading some information online I saw that autoclaves are designed to operate for 20 minutes, while pressure canners can support 10# pressure at 1000 feet elevation and below and 15# pressure above 1000 feet to 6000 feet elevation for as much as 240 minutes (fish in quarts).